Respuesta :

Answer: https://socratic.org/questions/how-do-you-simplify-cos-4x-sin-4x#618537

xenia168

Answer:

Step-by-step explanation:

FYI,

a² - b² = (a + b)(a - b)

f(x) = [tex]cos^{4} x[/tex] - [tex]sin^{4} x[/tex] = (cos²x + sin²x)(cos²x - sin²x) =

= (cos²x + sin²x)(cos x + sin x)(cos x - sin x)

If you need to simplify, then

f(x) = 1 × (cos²x - sin²x) = cos(2x)

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